Lack of Correlation Between Cerebral Vasomotor Reactivity and Flow-Mediated Dilation in Subjects Without Vascular Disease

Cerebral vasomotor reactivity (CVR) represents the capability of cerebral vessels to modify their caliber in response to a stimulus. Impaired CVR is associated with an increased risk for ischemic events in patients with carotid disease. Endothelial dysfunction is considered an important pathogenic factor for atherosclerosis and can be noninvasively assessed by flow-mediated vasodilation (FMD) evaluation. We aimed to evaluate both CVR and FMD in patients without histories of vascular disease in order to define a possible correlation. FMD was measured as brachial artery flow and diameter changes induced by transient ischemia. CVR to hypercapnia was assessed in all subjects by means of a breath-holding test and, in 20 subjects, by an additional CO2 inhalation test. In 30 healthy volunteers (60% women, mean age 56 ± 6 years), CVR and FMD did not appear to be correlated (p = 0.444). A strong association between CO2-induced CVR and breath-holding index was observed (p < 0.001). CVR and FMD represent 2 different modalities that evaluate vasomotor function. According to our data, they did not appear to correlate, probably due to physiologic differences between cerebral and peripheral vascular districts and the vasodilatory stimulus used. The carbon dioxide-induced CVR and breath-holding index appeared to be significantly associated.